1. Field of the Invention
This invention relates to a heat-sensitive recording head, and a method of manufacturing the same, and more particularly to a thick film type heat-sensitive recording head applied to a facsimile and a printer, and a method of manufacturing the same.
2. Description of the Prior Art
A heat-sensitive recording head is generally provided on a substrate with a heating resistor having a plurality of finely spaced heating portions, and electrodes for selectively applying a recording signal current to the heating portions of the heating resistor, and adapted to apply the heat, the quantity of which is in accordance with that of Joule heat of the heating resistor, to a recording medium and thereby carry out the recording of data. The conventional heat-sensitive recording heads include a thin film type heat-sensitive recording head and a thick film type heat-sensitive recording head, which are different in the materials and manufacturing methods for their heating resistors.
A thin film type heat-sensitive recording head is manufactured as disclosed in, for example, the specification of U.S. Pat. No. 4,343,986, by forming a resistor on a substrate by the evaporation or sputtering of a metal, and finishing the resistor to a desired shape by a photoetching means. This thin film type heat-sensitive recording head has excellent properties but the manufacturing method is complicated and requires a large number of manufacturing steps.
A thick film type heat-sensitive recording head is manufactured as disclosed in, for example, the specification of U.S. Pat. No. 4,203,025, by printing the surface of a substrate with a pattern of a resistor paste material by using a screen on which a desired pattern is formed in advance; and then dry-backing the paste material to form a desired resistor. This thick film type heat-sensitive recording head can be manufactured by a very simple method at a low cost as compared with a thin film type heat-sensitive recording head. However, the resistance value of each resistor widely scatters due to the shape errors thereof including the bending thereof caused by the electrodes, and the scatter of the width and intervals of the electrodes, and the material errors including the errors of the mixing ratio of a mixing material, such as a solvent. The calorific power of the heating portions of the heating resistor is proportional to V.sup.2 /R wherein V is an applied voltage; and R the resistance value of the heating resistor. Accordingly, the calorific power difference causes the unevenness of optical density, so that a heating resistor causing such an inconvenience does not sufficiently serve the purpose of reproducing, especially, an image of a high quality, such as an image of a high gradation of full color.